1. Technical Field
The present invention relates generally to the field of complementary metal oxide silicon technology, and in particular, to the interconnection of differentially doped diffusion regions.
2. Background Art
In complementary metal oxide silicon (CMOS) technology, the gate electrodes of n-channel and p-channel field effect transistors (FET) are interconnected such that for a given applied voltage, one of the two devices is off. In some CMOS circuits, it is also necessary to interconnect an n-type source/drain diffusion region to a p-type source/drain diffusion region. Conventionally, these diffusion interconnections are accomplished by, for example, using metal wires to connect the regions or by providing an isolation trench to connect the two regions.
U.S. Pat. No. 4,939,567, entitled "Trench Interconnection for CMOS Diffusion Regions," issued on Jul. 3, 1990, and assigned to International Business Machines Corp., describes a conductor filled trench used to couple an n-type diffusion region to a p-type diffusion region. The trench is disposed between a P+ diffusion region and an N+ diffusion region such that a conductive layer within the trench electrically couples the diffusion regions to one another. The conductor is insulated from the substrate by a thin dielectric layer located on the sidewalls and bottom of the trench.
In U.S. Pat. No. 4,983,544, entitled "Silicide Bridge Contact Process," issued on Jan. 8, 1991, and assigned to International Business Machines Corp., a method of forming a bridge contact between a source diffusion region and a conductor filled trench is described. The trench is coupled to a source diffusion region by depositing a layer of refractory metal, such as titanium, on the substrate's surface, and by sintering to form titanium silicide.
The above-described methods of interconnecting an n-type diffusion region and a p-type diffusion region require the addition of an additional element such as wire to connect the regions or a trench disposed between the regions which then needs to be interconnected to the diffusion regions. These additional elements add to process complexity and expense. Thus, there exists a need to form an interconnection between differentially doped diffusion regions without the use of additional elements. Further, a need exists to form an interconnection between differentially doped diffusion regions without utilizing separate mask and etch steps.